The present invention relates to building and wrapping a load, and more particularly to stretch wrapping a load.
Commercial products are often packaged together in a load and subsequently wrapped for transportation from a manufacturing facility. Machines that build a load of layers of products onto a pallet are generally known as palletizers. A conventional palletizer is fed product from an infeed conveyor and accumulates a single layer of product onto a plate. Once the layer is accumulated, the layer is deposited onto the pallet. This process is repeated until the desired number of layers are positioned on the pallet to build a load. Machines which then wrap the sides of a load with a web of stretch material to cover and contain the load are generally known as stretch wrapping machines. Upon completion of building a load of product on a pallet, the pallet is removed from the palletizer and transported to the stretch wrapper by a fork truck, an automated guided vehicle, a pallet car, a conveyor belt, or other transport mechanism.
Several problems can result from this process of building and wrapping a load of products, particularly when using deformed or unsquare load units. For example, typical load units include cardboard packaging material having flaps that fold over one another and interconnect to form a buldging load unit. As the load units are stacked, the deformations of the deformed, buldging packages become additive and can result in an unstable load.
As layers of these products are added, the load becomes more unstable, causing difficulty in transporting the load to a wrapping area or wrapping the load. Keeping the products and the layers of products in alignment particularly becomes more difficult as taller loads are built, moved, and wrapped. The forces exerted on the load by movement, the stretch wrap, and the centrifugal forces caused by rotation of the load during wrapping can result in misaligned product layers, and loads that will not stay together during transport or wrapping.
In addition, while stacking load units in columns produces a less crushable load, it can result in an unstable load. Therefore, load units typically are stacked in an interlocking brick-like configuration which provides more stability but which is more easily crushable because, in an interlocking brick-like configuration, the tops of the load units receive considerable forces that are unaligned with the edges of the load units. This requires the packaging of each load unit to be of greater strength than column stacking and results in more expensive, rigid packaging material than in column stacking.